Intraparticle FRET for Enhanced Efficiency of Two‐Photon Activated Photodynamic Therapy

: Photodynamic therapy (PDT) still faces two main problems on cancer therapy. One is how to improve PDT efficiency against hypoxic environment of tumors. The other one is how to overcome the limit of short wavelength light to increase PDT treatment depth. In this work, an intraparticle fluorescence resonance energy transfer (FRET) platform is designed to address these problems together. The nanoparticles are doped with multicomponents, such as catalase, two-photon dyes, and traditional photosensitizers, with a simple "one-pot" and green method. On the one hand, catalase can catalyze intracellular H2 O2 into O2 and promote PDT efficiency. One the other hand, photosensitizers can be excited indirectly by two-photon lasers through an intraparticle FRET mechanism, which results in deeper tissue penetration for PDT. These properties are verified through the material induced cytotoxicity in light or in dark and in vivo blocking blood-vessel experiment.